This invention relates to motor vehicle glazing, and particularly to a motor vehicle glazing assembly having a gasket ultrasonically welded to a sheet of thermoplastic glazing material. This invention also relates to thermoplastic motor vehicle glazing having a breakaway feature.
Motor vehicle glazing, which can be either glass or plastic, particularly stationary glazing such as a windshield or a rear window, is typically installed with a gasket surrounding the glazing material. The gasket performs several functions. First, it keeps the elements from entering into the motor vehicle around the edges of the glazing. Second, it cushions the glazing from the motor vehicle window frame, reducing the chance of breakage. The gasket is typically made from a flexible material, and it therefore also eases the installation of the glazing because it can be deformed to fit into the frame.
Originally, motor vehicle glazing gaskets were mated and bonded to both the glazing material and the frame at the time of installation of the glazing, using adhesives applied at that time. However, application of the gasket to the glazing at the point of installation is a messy and time-consuming operation.
It is known to apply the gasket to the glazing at an earlier stage in the vehicle assembly process using the same type of adhesive. Although this does not eliminate the need to use adhesives, it does shorten the time needed to install the glazing on the vehicle.
It is also known to provide a gasket of thermoplastic material with an electrical resistance heating element embedded in it. The gasket is positioned so that it contacts both the glazing and the frame and may or may not cover the edges of the glazing. An electric current is then passed through the heating element to melt the gasket so that it bonds to both the frame and the glazing. This method avoids the use of adhesive but is a very time-consuming step in the assembly process.
In another known method, a gasket is injection molded directly onto the glazing material without using adhesive. This eliminates the use of adhesive and also eliminates the gasket-applying step during installation. However, motor vehicle glazing comes in all shapes, sizes and contours. An injection molding machine can only be set for one size, shape and contour, so separate machines are required for each different piece of glazing, resulting in great expense and capital investment.
Motor vehicle glazing made of silicate glass is generally made of laminated safety glass which, when shattered, breaks into small rounded pieces. However, thermoplastic glazing does not have such a characteristic.
It would be desirable to economically reduce the use of adhesives in motor vehicle glazing installations. It would also be desirable to minimize the time needed to install motor vehicle glazing. Finally, it would be desirable to impart to thermoplastic motor vehicle glazing a characteristic similar to that of safety glass.